1. Field of the Invention
The present invention relate to a stirling engine. More particularly, it relates to a vibration-reducing apparatus capable of reducing vibrations and deadening noises caused in the operation of the stirling engine by using an additional weight.
2. Discussion of Background
FIG. 7 is a longitudinal cross-sectional view showing the structure of a typical power transmitting unit in a conventional stirling engine with a crank mechanism. In FIG. 7, a reference numeral 1 designates a crank casing in which an assembly of the power transmitting unit for the stirling engine is enclosed. A numeral 2 designates a first flange fixed to the crank casing 1 by means of fastening elements such as bolts which are engaged with holes formed in the crank casing 1, a numeral 3 designates a bearing housing connected to the crank casing 1 in the same manner as the flange 2, a numeral 4 designates a second flange connected to the crank casing 1 through the bearing flange 3 by means of fastening elements, a numeral 5 designates a first bearing held by the bearing housing 3, a numeral 6 designates a second bearing held by the first flange 2 and a numeral 7 designates a crank shaft supported by the first and second bearings 5, 6 in a freely rotatable manner, the crank shaft 7 transmitting a power produced in the stirling engine to an outer device. A mechanical seal 8 is mounted on the crank shaft 7 to prevent gas enclosed in the crank casing 1 from escaping. A pair of balance weights 9 and 10 are respectively fixed to the crank shaft 7 so as to balance the crank shaft 7 of the stirling engine when it is rotated.
A numeral 14 designates a lubricating oil received in the bottom of the crank casing 1, which is to lubricate each moving part of the stirling engine, and a numeral 15 designates a splasher for splashing the lubricating oil, the splasher being attached to a connecting rod 13 for a displacer or connecting rods 11, 12 for a power piston, which are connected to the crank shaft 7 by means of a bearing. A crosshead 21 is connected to the connecting rods 11, 12. The crosshead 21 is also connected to a power piston 18 and a rod 22 for the power piston. The outer circumferential surface of the crosshead 21 is in contact with the inner surface of the cylinder 20 as a bearing so as to be in a reciprocatedly slidable manner.
The connecting rod 13 for displacer is connected to the crank shaft 7 by means of a bearing in a freely rotatable manner. A piston rod 17 for displacer is connected to the connecting rod 13 by means of a piston pin 16. The piston rod 17 is passed through each central through hole of the crosshead 21, the power piston rod 22 and the power piston 18 and is connected to a displacer piston 19.
The cylinder 20 is mounted on the upper part of the crank casing 1 so that it receives the displacer piston 19 and the power piston 18 to allow their reciprocate-sliding movements.
In FIG. 7, the structure of the combustion unit and the heat exchanging unit of the stirling engine is omitted from the figure.
The operation of the conventional stirling engine will be described.
In the so called one-cylinder-two piston serially arranged crank shaft type stirling engine, change in pressure produced in the cylinder 20 causes the power piston to produce a force, which is transmitted to the connecting rods 11, 12 by the power piston rod 22 and the crosshead 21, whereby the work of rotation is taken at the outside through the crank shaft 7.
A part of the rotational work is transmitted to the displacer piston 19 to induce a reciprocating movement so as to function as a stirling engine.
FIG. 6 is a schematic view showing the construction of a typical direct-acting type stirling engine. The direct-acting type stirling engine is different from the crank shaft type stirling engine as shown in FIG. 7, and it allows to take out a power obtained by the reciprocating movements of the displacer piston 19 without using the crank mechanism. In FIG. 6, the same reference numerals as in FIG. 7 designate the same or corresponding parts. The cylinder 20 contains the displacer piston 19 and the power piston 18 in the same manner as the crank shaft type stirling engine. A driving shaft 26 is directly connected to the power piston 18. A numeral 23 designates a direct-acting type electric generator which is adapted to convert a mechanical power produced by the power piston 18 into an electric power. In the electric generator 23, there are a plurality of permanent magnets arranged in a cylinderical form, each being to be magnetized in the radial direction, a yoke 23b supporting the permanent magnets 23a to form a magnetic circuit, the yoke being movable with the power piston 18, a direct-acting driving part 23 contisting of mechanical springs which assures to form a balancing point of movement for a movable part contisting of the power piston 18, the driving shaft 26, the permanent magnets 23a and the yoke 23b, and a coil 23d inserted in a magnetic air gap formed between the permanent magnets 23 a and the yoke 23d, the coil being fixed to a casing 27 which is, in turn, connected to the cylinder 20.
In the conventional direct-acting type stirling engine having the above-mentioned construction, change in pressure produced in the cylinder 20 acts on the power piston 18 to thereby cause reciprocating movements of the yoke 23b with the permanent magnets 23a through the driving shaft 26. In this case, a magnetic flux formed by the permanent magnets 23a alternately crosses the coil 23d, whereby an electric power is induced in the coil 23d by electromagnetic function. The electric power is taken outside as a result of the function of the stirling engine.
In the conventional direct-acting type stirling engine having the construction as described above, a force of inertia caused by the reciprocating movements of the direct-acting driving part contisting of the power piston 18, the permenent magnets 23a and the yoke 23b is very large. The force of inertia caused by the reciprocating movements is transmitted to the casing 27 by means of the springs 23c. The cylinder 20 is supported by a frame 25 through a elastic mount 24 so as not to transmit vibrations to the frame 25. However, the force of inertia from the direct-acting driving part is great, and a transmitting force to the frame 25 is also large. As a result, vibrations in the engine become large.